This invention is directed toward pressure measurements in fluids which are held in containers. Of particular interest are fluid pressure detectors and detector systems which are capable of surviving harsh environments, including substantial shock and vibration, while maintaining accuracy in pressure readings.
Additionally, the measurement of fluid pressures in the pressure vessels of nuclear reactors is of interest. For information regarding nuclear reactors, refer, for example, to Energy Technology Handbook, edited by Douglas M. Considine and published by McGraw Hill Book Company in 1977.
The prior art includes electromechanical detectors sensitive to applied pressure and producing an electrical indication representative of pressure. One such device involves a loaded membrane acting as a variable capacitance in a tuned circuit. Other pressure detectors use vibrating wires damped in their medium of operation.
There are also detectors in the prior art which note mechanically the deflection of a loaded diaphragm exposed to the pressure carrying medium under measurement. The diaphragm then mechanically unbalances a wheatstone bridge and the degree of imbalance represents the amount of pressure. The prior art further includes devices electromagnetically compensating for the deflection of the diaphragm. Yet another approach involves mechanically translating the deflection of the diaphragm into the movement of a rod through a system of springs, levers, and electrical controls.
However, the above indicated devices of the prior art are relatively complex, expensive, and generally unreliable. Frequently, they are temperature dependent and are subject to drift related problems.
Furthermore, existing pressure detectors are typically unstable, that is subject to undesirable changes in hostile environments and are accordingly of questionable dependability. For example, when such devices are subject to excessive stress, they may irreversably deform or be the subject of internal failure. Even more significantly, there is usually no means of assessing the integrity of the detector in situ. This problem is exacerbated, because the electronics associated with the detector are often mounted within the detector and are thus subject to the very harsh or uncontrolled environment actually being measured. This limits the useful life of the detector as a whole.
For useful additional background regarding detectors of the prior art, see Quartly, C. J., in Square-Loop Ferrite Circuitry by Illiffe Books Ltd., London, 1962; and Stucki, F. F. at Sensor & Measuring Systems Symposium in "A High Speed Ferrimagnetic Macrotransducer", June 1968.